U.S. patent application number 13/294085 was filed with the patent office on 2012-05-17 for corrosion inhibiting composition.
Invention is credited to Donald E. Kiely, Kylie Kramer-Presta, Tyler N. Smith.
Application Number | 20120119152 13/294085 |
Document ID | / |
Family ID | 45048270 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120119152 |
Kind Code |
A1 |
Smith; Tyler N. ; et
al. |
May 17, 2012 |
CORROSION INHIBITING COMPOSITION
Abstract
This invention relates to novel corrosion inhibitors which are
capable of sequestering metal ions such as calcium and magnesium
and are derived in part from renewable carbohydrate feedstocks. The
corrosion inhibitors are mixtures containing one or more
hydroxycarboxylic acid salts and one or more suitable oxoacid anion
salts.
Inventors: |
Smith; Tyler N.; (Missoula,
MT) ; Kiely; Donald E.; (Missoula, MT) ;
Kramer-Presta; Kylie; (Missoula, MT) |
Family ID: |
45048270 |
Appl. No.: |
13/294085 |
Filed: |
November 10, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61412706 |
Nov 11, 2010 |
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Current U.S.
Class: |
252/389.4 ;
252/389.52; 252/389.54; 252/389.62; 252/396 |
Current CPC
Class: |
C02F 2303/08 20130101;
C11D 3/0073 20130101; C11D 3/046 20130101; C23F 11/08 20130101;
C23F 11/126 20130101; C02F 5/105 20130101; C11D 3/2086 20130101;
C23F 11/06 20130101 |
Class at
Publication: |
252/389.4 ;
252/396; 252/389.62; 252/389.52; 252/389.54 |
International
Class: |
C09K 15/06 20060101
C09K015/06; C09K 15/20 20060101 C09K015/20; C09K 15/32 20060101
C09K015/32 |
Claims
1. A corrosion inhibiting composition for metal comprising a
mixture of at least one salt of a hydroxycarboxylic acid and at
least one salt of an oxoacid anion.
2. The corrosion inhibition composition of claim 1, wherein the at
least one salt of a hydroxycarboxylic acid comprises a salt of
glucaric acid, a salt of xylaric acid, a salt of galactaric acid
and combinations thereof.
3. The corrosion inhibiting composition of claim 2, wherein the at
least one salt of a hydroxycarboxylic acid comprises glucaric
acid.
4. The corrosion inhibiting composition of claim 3, wherein the at
least one salt of a glucaric acid comprises disodium glucarate,
sodium potassium glucarate, dipotassium glucarate, zinc glucarate,
diammonium glucarate, and combinations thereof.
5. The corrosion inhibiting composition of claim 1, wherein the
composition comprises from about 50% to about 99% by weight of said
at least one salt of hydroxycarboxylic acid and from about 1% to
about 50% by weight of at least one salt of an oxoacid anion.
6. The corrosion inhibiting composition of claim 1, wherein the
composition comprises from about 70% to about 90% by weight of said
at least one salt of hydroxycarboxylic acid and from about 10% to
about 30% by weight of at least one salt of an oxoacid anion.
7. The corrosion inhibiting composition of claim 1, wherein the
composition comprises from about 75% to about 85% by weight of said
at least one salt of hydroxycarboxylic acid and from about 15% to
about 25% by weight of at least one salt of an oxoacid anion.
8. The corrosion inhibiting composition of claim 3, wherein the
composition comprises from about 30% to about 60% by weight of said
salt of glucaric acid and from about 5% to about 40% by weight of
at least one salt of an oxoacid anion.
9. The corrosion inhibiting composition of claim 8, wherein the
composition comprises from about 40% to about 50% by weight of said
salt of glucaric acid and from about 15% to about 25% by weight of
at least one salt of an oxoacid anion.
10. The corrosion inhibiting composition of claim 3, wherein the
composition comprises from about 15% to about 50% by weight of said
salt of glucaric acid and from about 5% to about 40% by weight of
at least one salt of an oxoacid anion.
11. The corrosion inhibiting composition of claim 10, wherein the
composition comprises from about 28% to about 36% by weight of said
salt of glucaric acid and from about 15% to about 25% by weight of
at least one salt of an oxoacid anion.
12. The corrosion inhibiting composition of claim 1, wherein the at
least one salt of a hydroxycarboxylic acid comprises about 30% to
about 75% by weight of the at least one glucarate salt, about 0% to
about 20% by weight of the at least one gluconate salt, about 0% to
about 10% by weight of the at least one 5-keto-gluconate salt,
about 0% to about 10% by weight of the at least one tartrate salt,
about 0% to 10% by weight of the at least one tartronate salt, and
about 0% to 10% by weight of the at least one glycolate salt.
13. The corrosion inhibiting composition of claim 1, wherein the at
least one salt of a hydroxycarboxylic acid comprises about 40% to
about 60% by weight of the at least one glucarate salt, about 5% to
about 15% by weight of the at least one gluconate salt, about 3% to
about 9% by weight of the at least one 5-keto-gluconate salt, about
5% to about 10% by weight of the at least one tartrate salt about
5% to 10% by weight of the at least one tartronate salt, and about
1% to 5% by weight of the at least one glycolate salt.
14. The corrosion inhibiting composition of claim 1, wherein the at
least one salt of a hydroxycarboxylic acid comprises 45% to about
55% by weight of the at least one glucarate salt, about 10% to
about 15% by weight of the at least one gluconate salt, about 4% to
about 6% by weight of the at least one 5-keto-gluconate salt, about
5% to about 7% by weight of the at least one tartrate salt, about
5% to 7% by weight of the at least one tartronate salt, and about
3% to 5% by weight of the at least one glycolate salt.
15. The corrosion inhibition composition of claim 1, wherein the at
least one salt of a hydroxycarboxylic acid comprises about 50% by
weight of the at least one glucarate salt, about 15% by weight of
the at least one gluconate salt, about 4% by weight of the at least
one 5-keto-gluconate salt, about 6% by weight of the at least one
tartrate salt, about 6% by weight of the at least one tartronate
salt, and about 5% by weight of the at least one glycolate
salt.
16. The corrosion inhibiting composition of claim 2, wherein the at
least one salt of a hydroxycarboxylic acid comprises about 30% to
about 75% by weight of the at least one glucarate salt, about 0% to
about 20% by weight of the at least one gluconate salt, about 0% to
about 10% by weight of the at least one 5-keto-gluconate salt,
about 0% to about 10% by weight of the at least one tartrate salt,
about 0% to 10% by weight of the at least one tartronate salt, and
about 0% to 10% by weight of the at least one glycolate salt.
17. The corrosion inhibiting composition of claim 2, wherein the at
least one salt of a hydroxycarboxylic acid comprises about 40% to
about 60% by weight of the at least one glucarate salt, about 5% to
about 15% by weight of the at least one gluconate salt, about 3% to
about 9% by weight of the at least one 5-keto-gluconate salt, about
5% to about 10% by weight of the at least one tartrate salt about
5% to 10% by weight of the at least one tartronate salt, and about
1% to 5% by weight of the at least one glycolate salt.
18. The corrosion inhibiting composition of claim 2, wherein the at
least one salt of a hydroxycarboxylic acid comprises about 45% to
about 55% by weight of the at least one glucarate salt, about 10%
to about 15% by weight of the at least one gluconate salt, about 4%
to about 6% by weight of the at least one 5-keto-gluconate salt,
about 5% to about 7% by weight of the at least one tartrate salt,
about 5% to 7% by weight of the at least one tartronate salt, and
about 3% to 5% by weight of the at least one glycolate salt.
19. The corrosion inhibition composition of claim 2, wherein the at
least one salt of a hydroxycarboxylic acid comprises 50% by weight
of the at least one glucarate salt, about 15% by weight of the at
least one gluconate salt, about 4% by weight of the at least one
5-keto-gluconate salt, about 6% by weight of the at least one
tartrate salt, about 6% by weight of the at least one tartronate
salt, and about 5% by weight of the at least one glycolate
salt.
20. The corrosion inhibiting composition of claim 2, wherein the at
least one salt of a hydroxycarboxylic acid comprises xylaric
acid.
21. The corrosion inhibiting composition of claim 20, wherein the
at least one salt of xylaric acid comprises disodium xylarate,
sodium potassium xylarate, dipotassium xylarate, zinc xylarate,
diammonium xylarate and combinations thereof.
22. The corrosion inhibiting composition of claim 20, wherein the
composition comprises from about 15% to about 50% by weight of said
salt of xylaric acid and from about 5% to about 40% by weight of at
least one salt of an oxoacid anion.
23. The corrosion inhibiting composition of claim 22, wherein the
composition comprises from about 20% to about 45% by weight of said
salt of xylaric acid and from about 10% to about 30% by weight of
at least one salt of an oxoacid anion.
24. The corrosion inhibiting composition of claim 23, wherein the
composition comprises from about 25% to about 40% by weight of said
salt of xylaric acid and about 15% to about 25% by weight of at
least one salt of an oxoacid anion.
25. The corrosion inhibiting composition of claim 2, wherein the at
least one salt of a hydroxycarboxylic acid comprises galactaric
acid.
26. The corrosion inhibiting composition of claim 26, wherein the
at least one salt of galactaric acid comprises dipotassium
galactarate, disodium galactarate, sodium potassium galactarate,
zinc galactarate, diammonium galactarate and combinations
thereof.
27. The corrosion inhibiting composition of claim 26, wherein the
composition comprises from about 15% to about 50% by weight of said
salt of galactaric acid and from about 5% to about 40% by weight of
at least one salt of an oxoacid anion.
28. The corrosion inhibiting composition of claim 23, wherein the
composition comprises from about 30% to about 60% by weight of said
salt of galactaric acid and from about 10% to about 30% by weight
of at least one salt of an oxoacid anion.
29. The corrosion inhibiting composition of claim 24, wherein the
composition comprises from about 40% to about 50% by weight of said
salt of galactaric acid and about 15% to about 25% by weight of at
least one salt of an oxoacid anion.
30. The corrosion inhibiting composition of claim 1, wherein the
salt of an oxoacid anion is sodium borate, potassium borate,
disodium octaborate, sodium metaborate, sodium molybdate, potassium
molybdate, sodium aluminate, potassium aluminate, sodium stannate,
potassium stannate, sodium germanate, potassium germanate, sodium
antimonite, potassium antimonite, and combinations thereof.
31. A corrosion inhibiting composition for metal comprising a
mixture of from about 75% to about 85% by weight of at least one
salt of a hydroxycarboxylic acid and from about 15% to about 25% of
at least one salt of an oxoacid anion.
32. The corrosion inhibiting composition of claim 23, wherein said
at least one salt of a hydroxycarboxylic acid comprises from about
40% to about 50% by weight of a salt of glucaric acid.
33. The corrosion inhibiting composition of claim 24, wherein said
salt of glucaric acid comprises disodium glucarate, sodium
potassium glucarate, dipotassium glucarate, zinc glucarate,
diammonium glucarate and combinations thereof.
34. The corrosion inhibiting composition of claim 23, wherein said
at least one salt of a hydroxycarboxylic acid comprises from about
25% to about 40% by weight of a salt of xylaric acid.
35. The corrosion inhibiting composition of claim 26, wherein said
salt of xylaric acid comprises disodium xylarate, sodium potassium
xylarate, dipotassium xylarate, zinc xylarate, diammonium xylarate
and combinations thereof.
36. The corrosion inhibiting composition of claim 23, wherein said
at least one salt of a hydroxycarboxylic acid comprises from about
40% to about 50% by weight of a salt of galactaric acid.
37. The corrosion inhibiting composition of claim 28, wherein said
salt of xylaric acid comprises dipotassium galactarate, disodium
galactarate, sodium potassium galactarate, zinc galactarate,
diammonium galactarate and combinations thereof.
38. The corrosion inhibiting composition of claim 31, wherein the
at least one salt of a hydroxycarboxylic acid comprises about 30%
to about 75% by weight of the at least one glucarate salt, about 0%
to about 20% by weight of the at least one gluconate salt, about 0%
to about 10% by weight of the at least one 5-keto-gluconate salt,
about 0% to about 10% by weight of the at least one tartrate salt,
about 0% to 10% by weight of the at least one tartronate salt, and
about 0% to 10% by weight of the at least one glycolate salt.
39. The corrosion inhibiting composition of claim 31, wherein the
at least one salt of a hydroxycarboxylic acid comprises about 40%
to about 60% by weight of the at least one glucarate salt, about 5%
to about 15% by weight of the at least one gluconate salt, about 3%
to about 9% by weight of the at least one 5-keto-gluconate salt,
about 5% to about 10% by weight of the at least one tartrate salt
about 5% to 10% by weight of the at least one tartronate salt, and
about 1% to 5% by weight of the at least one glycolate salt.
40. The corrosion inhibiting composition of claim 31, wherein the
at least one salt of a hydroxycarboxylic acid comprises about 45%
to about 55% by weight of the at least one glucarate salt, about
10% to about 15% by weight of the at least one gluconate salt,
about 4% to about 6% by weight of the at least one 5-keto-gluconate
salt, about 5% to about 7% by weight of the at least one tartrate
salt, about 5% to 7% by weight of the at least one tartronate salt,
and about 3% to 5% by weight of the at least one glycolate
salt.
41. The corrosion inhibition composition of claim 31, wherein the
at least one salt of a hydroxycarboxylic acid comprises about 50%
by weight of the at least one glucarate salt, about 15% by weight
of the at least one gluconate salt, about 4% by weight of the at
least one 5-keto-gluconate salt, about 6% by weight of the at least
one tartrate salt, about 6% by weight of the at least one
tartronate salt, and about 5% by weight of the at least one
glycolate salt.
Description
RELATED APPLICATION INFORMATION
[0001] This application claims priority to U.S. Provisional
Application No. 61/412,706 filed on Nov. 11, 2010, the contents of
which are herein incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention describes novel corrosion inhibitors which
are capable of sequestering metal ions such as calcium and
magnesium and are derived in part from renewable carbohydrate
feedstocks. The corrosion inhibitors are mixtures containing one or
more hydroxycarboxylic acid salts and one or more suitable oxoacid
anion salts. The hydroxycarboxylic acid salts can be readily
produced from carbohydrate and other polyol feedstocks through
chemical or biological oxidation.
BACKGROUND OF THE INVENTION
[0003] Hydroxycarboxylic acids and hydroxycarboxylic acid salts are
well recognized as corrosion inhibitors particularly effective in
inhibiting metal corrosion when the metal is in contact with water
or an aqueous solution. U.S. Pat. No. 2,529,178 to Nieland et al.
taught that these hydroxycarboxylic acids, or salts thereof, may
contain a single carboxylic acid function, as in the case of
gluconic acid (U.S. Pat. No. 2,529,178), or more than one
carboxylic acid functions as in the case of tartaric acid, a
hydroxydicarboxylic acid, or citric acid, a hydroxy tricarboxylic
acid (U.S. Pat. No. 2,529,177). Nieland et al. also taught that
hydroxycarboxylic acids, or salts thereof, with more than one
carboxylic acid functions, such as tartaric acid (U.S. Pat. No.
2,529,177), generally exhibit better corrosion inhibition
properties than do comparable hydroxymonocarboxylic acids, such as
gluconic acid (U.S. Pat. No. 2,529,178).
[0004] Hydroxycarboxylic acids have also been shown to inhibit
metal corrosion in aqueous salt brine such as sea water (Mor, 1971;
Mor, 1976; and Wrubl, 1984) or formulated brine solutions
(Kuczynski, 1979; Korzh, 1981; Sukhotin, 1982; and Abdallah, 1999),
and some are employed for specific applications, such as in
industrial cooling systems (Sukhotin, 1982).
[0005] In addition, hydroxycarboxylic acids and hydroxycarboxylic
acid salts have been described as chelating agents capable of
sequestering metal ions in solution (Mehltretter, 1953; Abbadi,
1999). Hydroxycarboxylic acid salts as sequestering agents for
metal ions such as calcium and magnesium, in general perform poorly
compared to common sequestering agents such as sodium
tripolyphosphate (STPP), ethylenediaminetriacetate (EDTA), or
nitrilotriacetate (NTA). In spite of low sequestering capacity,
hydroxycarboxylic acid salts are of interest because they are
typically biodegradable, non-toxic, and derived from renewable
resources such as carbohydrates. Therefore, the use
hydroxycarboxylic acid salts as replacement sequestering agents for
STPP and EDTA is advantageous, especially in applications where the
compounds may be discharged into the environment.
[0006] Many chemical compounds that have traditionally been used as
corrosion inhibitors and metal sequestering agents are phosphorus
based. Through environmental regulations, the use of phosphorus
compounds in applications where the material is discharged into
surface water continues to be restricted. These regulations have
created a need for environmentally acceptable materials for use as
corrosion inhibiting agents for a variety of applications. One area
of specific need centers around corrosion inhibiting agents which
are also capable of sequestering metal ions, specifically metal
ions like calcium and magnesium commonly found in tap water or
fresh ground water and which can lead to scale formation. In
particular, agents capable of both preventing corrosion and
inhibiting scale would be useful as builders in detergents or as
additives to process water used in industrial cooling towers and
boiler systems.
[0007] One application in which corrosion inhibitors which act as
sequestering agents are useful is in detergent formulations.
Detergents are cleaning mixtures composed primarily of surfactants,
builders, bleaching-agents, enzymes, and fillers. Two of the major
components are surfactants and builders. The surfactants are
responsible for emulsification of oil and grease while builders are
added to extend or improve the cleaning properties of the
surfactant. The builder can be a single substance or a mixture of
substances and commonly serve multiple functions. An important
builder function is the sequestration of metal cations, typically
calcium and magnesium cations in hard water. The builders act as
water softening agents by sequestering calcium and magnesium
cations and preventing the formation of water insoluble salts
between the metals and surfactants (soap scum). In the case of
laundry detergents, builders also help prevent the cations from
binding to cotton, a major cause of soil retention on cotton
fabrics. Other functions of builders include increasing alkalinity
of detergent solutions, deflocculating surfactant micelles, and
inhibiting corrosion.
[0008] The first builders used in commercial detergents were
phosphate salts and phosphate salt derivatives. Sodium
tripolyphosphate (STPP) was, at one time, the most common builder
in both consumer and industrial detergents. Phosphate builders are
also touted as corrosion inhibitors for the metal surfaces of
washing machines and dishwashers. Phosphates have been gradually
phased out of detergents over the past 40 years primarily due to
environmental concerns regarding discharge of phosphate rich waste
water into surface waters giving rise to eutrophication and
ultimately hypoxia (Lowe, 1978). High performance replacements for
phosphates in detergents are still sought after.
[0009] A second application area for corrosion inhibitors which
serve as sequestering agents is in the treatment of process water
used in industrial and institutional cooling tower and boiler
systems. Two of the primary problems associated with cooling tower
and boiler systems are corrosion and build-up of hard water scale
on metal surfaces. Corrosion shortens the life of the system
equipment while scaling decreases the efficiency of heat flow
across the metal surfaces. Historically, phosphates and
phosphonates have been used in water treatment as corrosion and
scale inhibitors. As with phosphate detergent builders, there is a
desire to replace phosphorus-based chemicals used in water
treatment. Accordingly, a need exists to have a corrosion inhibitor
which also serves as a sequestering agent, and which does not
incorporate phosphates or chemicals that have been deemed harmful
to the environment.
SUMMARY OF THE INVENTION
[0010] The present invention provides a corrosion inhibiting
composition for metal comprising a mixture of at least one salt of
a hydroxycarboxylic acid and at least one salt of a suitable
oxoacid anion. The at least one salt of a hydroxycarboxylic acid is
generally a salt of glucaric acid, a salt of xylaric acid, a salt
of galactaric acid or combinations thereof. Specifically, the at
least one salt of a glucaric acid may include disodium glucarate,
sodium potassium glucarate, dipotassium glucarate, zinc glucarate
or combinations thereof. In addition, the composition may comprise
from about 50% to about 99% by weight of the at least one salt of a
hydroxycarboxylic acid and from about 1% to about 50% by weight of
at least one salt of an oxoacid anion. The composition may also
include from about 70% to about 90% by weight of the at least one
salt of a hydroxycarboxylic acid and from about 10% to about 30% by
weight of at least one salt of an oxoacid anion. The composition
may additionally include from about 75% to about 85% by weight of
the at least one salt of a hydroxycarboxylic acid and from about
15% to about 25% by weight of at least one salt of a suitable
oxoacid anion.
[0011] The at least one salt of a hydroxycarboxylic acid may
include combinations of two or more carboxylate salt components.
One of the carboxylate salt components may include glucarates, such
as, disodium glucarate, sodium potassium glucarate, dipotassium
glucarate, diammonium glucarate, and zinc glucarate. The glucarate
salt component may include from about 30% to about 70% by weight of
the entire composition. Further, the glucarate salt component may
include from about 40% to about 60% by weight of the entire
composition.
[0012] Additionally, one of the carboxylate salt components of the
at least one salt of a hydroxycarboxylic acid may include
xylarates, such as sodium xylarate, disodium xylarate, sodium
potassium xylarate, dipotassium xylarate, diammonium xylarate, and
zinc xylarate. The xylarate salt component may include from about
30% to about 70% by weight of the entire composition. Further, the
xylarate salt component may include from about 40% to about 60% by
weight of the entire composition.
[0013] Further, one of the carboxylate salt components of the at
least one salt of a hydroxycarboxylic acid may include
galactarates, such as sodium galactarate, disodium galactarate,
sodium potassium galactarate, dipotassium galactarate, diammonium
galactarate, and zinc galactarate. The galactarate salt component
may include from about 30% to about 70% by weight of the entire
composition. Further, the galactarate component may include from
about 40% to about 60% by weight of the entire composition.
[0014] With respect to the at least one salt of a hydroxycarboxylic
acid, the composition can comprises about 30% to about 75% by
weight of the at least one glucarate salt, about 0% to about 20% by
weight of the at least one gluconate salt, about 0% to about 10% by
weight of the at least one 5-keto-gluconate salt, about 0% to about
10% by weight of the at least one tartrate salt, about 0% to 10% by
weight of the at least one tartronate salt, and about 0% to 10% by
weight of the at least one glycolate salt. Alternatively, the
composition can comprise about 40% to about 60% by weight of the at
least one glucarate salt, about 5% to about 15% by weight of the at
least one gluconate salt, about 3% to about 9% by weight of the at
least one 5-keto-gluconate salt, about 5% to about 10% by weight of
the at least one tartrate salt about 5% to 10% by weight of the at
least one tartronate salt, and about 1% to 5% by weight of the at
least one glycolate salt. In still yet another alternative, the
composition can comprise about 45% to about 55% by weight of the at
least one glucarate salt, about 10% to about 15% by weight of the
at least one gluconate salt, about 4% to about 6% by weight of the
at least one 5-keto-gluconate salt, about 5% to about 7% by weight
of the at least one tartrate salt, about 5% to 7% by weight of the
at least one tartronate salt, and about 3% to 5% by weight of the
at least one glycolate salt. In still yet another alternative, the
composition can comprise about 50% by weight of the at least one
glucarate salt, about 15% by weight of the at least one gluconate
salt, about 4% by weight of the at least one 5-keto-gluconate salt,
about 6% by weight of the at least one tartrate salt, about 6% by
weight of the at least one tartronate salt, and about 5% by weight
of the at least one glycolate salt.
[0015] In an alternative embodiment, the current invention
comprises a corrosion inhibiting composition for metal comprising a
mixture of from about 75% to about 85% by weight of at least one
salt of a hydroxycarboxylic acid and from about 15% to about 25% of
at least one salt of a suitable oxoacid anion. The at least one
salt of a hydroxycarboxylic acid may include from about 40% to
about 60% by weight of a salt of glucaric acid. Additionally, the
salt of glucaric acid may include, disodium glucarate, sodium
potassium glucarate, dipotassium glucarate, diammonium glucarate,
zinc glucarate, and combinations thereof.
[0016] Moreover, the at least one salt of a hydroxycarboxylic acid
may alternatively include from about 30% to about 70% by weight of
a salt of xylaric acid. The salt of xylaric acid may include,
disodium xylarate, sodium potassium xylarate, dipotassium xylarate,
diammonium xylarate, zinc xylarate, and combinations thereof.
[0017] Further, the at least one salt of a hydroxycarboxylic acid
may include from about 30% to about 70% by weight of a salt of
galactaric acid. The salt of galactaric acid may include, disodium
glucarate, sodium potassium glucarate, dipotassium glucarate, zinc
glucarate, diammonium galactarate, and combinations thereof.
[0018] In addition, the at least one salt of a hydroxycarboxylic
acid used in the composition can comprise a mixture of about 30% to
about 75% by weight of the at least one glucarate salt, about 0% to
about 20% by weight of the at least one gluconate salt, about 0% to
about 10% by weight of the at least one 5-keto-gluconate salt,
about 0% to about 10% by weight of the at least one tartrate salt,
about 0% to 10% by weight of the at least one tartronate salt, and
about 0% to 10% by weight of the at least one glycolate salt.
Alternatively, the at least one salt of a hydroxycarboxylic acid
used in the composition can comprise a mixture of about 40% to
about 60% by weight of the at least one glucarate salt, about 5% to
about 15% by weight of the at least one gluconate salt, about 3% to
about 9% by weight of the at least one 5-keto-gluconate salt, about
5% to about 10% by weight of the at least one tartrate salt about
5% to 10% by weight of the at least one tartronate salt, and about
1% to 5% by weight of the at least one glycolate salt. In still yet
another alternative, the at least one salt of a hydroxycarboxylic
acid used in the composition can comprise a mixture of about 45% to
about 55% by weight of the at least one glucarate salt, about 10%
to about 15% by weight of the at least one gluconate salt, about 4%
to about 6% by weight of the at least one 5-keto-gluconate salt,
about 5% to about 7% by weight of the at least one tartrate salt,
about 5% to 7% by weight of the at least one tartronate salt, and
about 3% to 5% by weight of the at least one glycolate salt. In
still yet another alternative, the at least one salt of a
hydroxycarboxylic acid can comprise a mixture of about 50% by
weight of the at least one glucarate salt, about 15% by weight of
the at least one gluconate salt, about 4% by weight of the at least
one 5-keto-gluconate salt, about 6% by weight of the at least one
tartrate salt, about 6% by weight of the at least one tartronate
salt, and about 5% by weight of the at least one glycolate
salt.
[0019] Suitable salts of oxoacid anions include sodium and
potassium salts of borate, aluminate, stannate, germanate,
molybdate, antimonate and combinations thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0020] This invention describes novel corrosion inhibitors
comprising mixtures of hydroxycarboxylic acid salts and suitable
salts of oxoacid anions. Hydroxycarboxylic acids are compounds
which contain one or more hydroxyl groups as well as one or more
carboxylic acid functionalities. The hydroxyl groups of these
compounds are capable of forming esters when combined with suitable
salts of oxoacid anions in water. In addition, these oxoacid anion
esters of hydroxycarboxylic acids have been shown to form stable,
water soluble complexes with metal ions such as calcium and
magnesium, as opposed to hydroxycarboxylic acids alone which
typically form water insoluble salts with many metal ions. Thus,
the combination of corrosion inhibiting properties and metal
sequestering properties of the current invention make mixtures of
oxoacid anion salts and hydroxycarboxylic acid salts attractive for
use as scale inhibitors and detergent builders.
[0021] As used herein, the term "hydroxycarboxylic acid" can
generally be considered any oxidation derivative of carbohydrates
or other polyols. The term polyol is generally defined as any
organic compound with two or more alcohol hydroxyl groups. Suitable
carbohydrates or polyols for oxidation include: simple aldoses and
ketoses such as glucose, xylose or fructose; simple polyols such as
glycerol, sorbitol or mannitol; reducing disaccharides such as
maltose, lactose, or cellobiose; reducing oligosaccharides such as
maltotriose, maltotetrose, or maltotetralose; nonreducing
carbohydrates such as sucrose, trehalose and stachyose; mixtures of
monosaccharides and oligosaccharides (that may include
disaccharides); glucose syrups with different dextrose equivalent
values; polysaccharides such as, but not limited to, starch,
cellulose, arabinogalactans, xylans, mannans, fructans,
hemicelluloses; mixtures of carbohydrates and other polyols that
include one or more of the carbohydrates or polyols listed above.
One skilled in the art will appreciate that compounds with two or
more carboxylic acid groups tend to perform better as corrosion
inhibitors than those containing only one carboxylic acid group.
Specific examples of hydroxycarboxylic acids that may be used in
the current invention include, but are not limited to glucaric
acid, xylaric acid, galactaric acid, gluconic acid, tartaric acid,
tartronic acid, glycolic acid, glyceric acid, and combinations
thereof. In one embodiment, the hydroxycarboxylic acid includes
glucaric acid, xylaric acid, and galactaric acid. Additionally, one
skilled in the art will appreciate that the hydroxycarboxylic acids
of the current invention encompasses all conceivable stereoisomers,
including diastereomers and enantiomers, in substantially pure form
as well as in any mixing ratio, including the racemates of the
hydroxycarboxylic acids.
[0022] In general, the compositions of the current invention
comprise from about 1% to about 99% by weight of the at least one
salt of a hydroxycarboxylic acid and from about 1% to about 99% by
weight of at least one salt of a suitable oxoacid anion. In one
embodiment, the composition includes from about 50% to about 99% by
weight of the at least one salt of a hydroxycarboxylic acid and
from about 1% to about 99% by weight of the at least one salt of an
oxoacid anion. In a further embodiment, the composition includes
from about 60% to about 95% by weight of the at least one salt of a
hydroxycarboxylic acid and from about 5% to about 40% by weight of
the at least one salt of an oxoacid anion. In still another
embodiment, the composition includes from about 70% to about 90% by
weight of the at least one salt of a hydroxycarboxylic acid and
from about 10% to about 30% by weight of the at least one salt of
an oxoacid anion. In an additional embodiment, the composition
includes from about 75% to about 85% by weight of the at least one
salt of a hydroxycarboxylic acid and from about 15% to about 25% by
weight of the at least one salt of an oxoacid anion. In yet another
embodiment, the composition comprises about 80% by weight of the at
least one salt of a hydroxycarboxylic acid and about 20% by weight
of the at least one salt of an oxoacid anion. It should be noted
that the concentrations stated herein refer to the cumulative
concentration of all carboxylate salts comprising the at least one
salt of a hydroxycarboxylic acid component, and that a single
carboxylate salt (wherein the hydroxycarboxylate salt component
comprises two or more carboxylate salts) may comprise less than the
stated concentration.
[0023] The corrosion inhibiting compositions of the current
invention comprise the salt form of the hydroxycarboxylic acids
discussed herein. One of skill in the art will appreciate that
salts are generally the compounds that arise from the
neutralization reaction of an acid and a base. Any oxidation
derivative of a carbohydrate or other polyol may be incorporated in
its salt form into the current invention. Non-limiting examples of
hydroxycarboxylic acid salts include disodium glucarate, sodium
potassium glucarate, dipotassium glucarate, dilithium glucarate,
lithium sodium glucarate, lithium potassium glucarate, zinc
glucarate, diammonium glucarate, disodium xylarate, sodium
potassium xylarate, dipotassium xylarate, dilithium xylarate,
lithium sodium xylarate, lithium potassium xylarate, zinc xylarate,
ammonium xylarate sodium gluconate, potassium gluconate, lithium
gluconate, zinc gluconate, ammonium gluconate, disodium
galactarate, sodium potassium galactarate, dipotassium galactarate,
dilithium galactarate, lithium sodium galactarate, lithium
potassium galactarate, zinc galactarate, diammonium galactarate,
disodium tartrate, sodium potassium tartrate, dipotassium tartrate,
dilithium tartrate, lithium sodium tartrate, lithium potassium
tartrate, zinc tartrate, diammonium tartrate, disodium tartronate,
sodium potassium tartronate, dipotassium tartronate, dilithium
tartronate, lithium sodium tartronate, lithium potassium
tartronate, zinc tartronate, diammonium tartronate, sodium
glycolate, potassium glycolate, lithium glycolate, zinc glycolate,
ammonium glycolate, sodium glycerate, potassium glycerate, lithium
glycerate, zinc glycerate, ammonium glycerate, and combinations
thereof. In another embodiment, the hydroxycarboxylic acid may
include, but is not limited to, disodium glucarate, sodium
potassium glucarate, dipotassium glucarate, zinc glucarate,
disodium xylarate, sodium potassium xylarate, dipotassium xylarate,
zinc xylarate, disodium galactarate, sodium potassium galactarate,
dipotassium galactarate, zinc galactarate, diammonium xylarate, and
combinations thereof.
[0024] In one aspect, with respect to the at least one salt of a
hydroxycarboxylic acid, the corrosion inhibiting compositions of
the present invention comprise about 30% to about 75% by weight of
the at least one glucarate salt, about 0% to about 20% by weight of
the at least one gluconate salt, about 0% to about 10% by weight of
the at least one 5-keto-gluconate salt, about 0% to about 10% by
weight of the at least one tartrate salt, about 0% to 10% by weight
of the at least one tartronate salt, and about 0% to 10% by weight
of the at least one glycolate salt. Alternatively, the composition
comprises about 40% to about 60% by weight of the at least one
glucarate salt, about 5% to about 15% by weight of the at least one
gluconate salt, about 3% to about 9% by weight of the at least one
5-keto-gluconate salt, about 5% to about 10% by weight of the at
least one tartrate salt about 5% to 10% by weight of the at least
one tartronate salt, and about 1% to 5% by weight of the at least
one glycolate salt. In still yet another alternative, the
composition comprises about 45% to about 55% by weight of the at
least one glucarate salt, about 10% to about 15% by weight of the
at least one gluconate salt, about 4% to about 6% by weight of the
at least one 5-keto-gluconate salt, about 5% to about 7% by weight
of the at least one tartrate salt, about 5% to 7% by weight of the
at least one tartronate salt, and about 3% to 5% by weight of the
at least one glycolate salt. In still yet another alternative, the
composition comprises about 50% by weight of the at least one
glucarate salt, about 15% by weight of the at least one gluconate
salt, about 4% by weight of the at least one 5-keto-gluconate salt,
about 6% by weight of the at least one tartrate salt, about 6% by
weight of the at least one tartronate salt, and about 5% by weight
of the at least one glycolate salt.
[0025] In another aspect, the at least one salt of a
hydroxycarboxylic acid in the corrosion inhibiting composition
comprises a mixture of about 30% to about 75% by weight of the at
least one glucarate salt, about 0% to about 20% by weight of the at
least one gluconate salt, about 0% to about 10% by weight of the at
least one 5-keto-gluconate salt, about 0% to about 10% by weight of
the at least one tartrate salt, about 0% to 10% by weight of the at
least one tartronate salt, and about 0% to 10% by weight of the at
least one glycolate salt. Alternatively, the at least one salt of a
hydroxycarboxylic acid comprises a mixture of about 40% to about
60% by weight of the at least one glucarate salt, about 5% to about
15% by weight of the at least one gluconate salt, about 3% to about
9% by weight of the at least one 5-keto-gluconate salt, about 5% to
about 10% by weight of the at least one tartrate salt about 5% to
10% by weight of the at least one tartronate salt, and about 1% to
5% by weight of the at least one glycolate salt. In still yet
another alternative, the at least one salt of a hydroxycarboxylic
acid comprises a mixture of about 45% to about 55% by weight of the
at least one glucarate salt, about 10% to about 15% by weight of
the at least one gluconate salt, about 4% to about 6% by weight of
the at least one 5-keto-gluconate salt, about 5% to about 7% by
weight of the at least one tartrate salt, about 5% to 7% by weight
of the at least one tartronate salt, and about 3% to 5% by weight
of the at least one glycolate salt. In still yet another
alternative, In still yet another alternative, the at least one
salt of a hydroxycarboxylic acid comprises a mixture of about 50%
by weight of the at least one glucarate salt, about 15% by weight
of the at least one gluconate salt, about 4% by weight of the at
least one 5-keto-gluconate salt, about 6% by weight of the at least
one tartrate salt, about 6% by weight of the at least one
tartronate salt, and about 5% by weight of the at least one
glycolate salt.
[0026] The hydroxycarboxylic acids of the current invention may be
produced according to any methods currently known in the art. The
currently employed commercial methods of preparation of the common
hydroxycarboxylic acids or salts thereof are principally
biologically induced transformations or fermentations, as for
example in the production of tartaric acid (U.S. Pat. No.
2,314,831), gluconic acid (U.S. Pat. No. 5,017,485), and citric
acid (U.S. Pat. No. 3,652,396). Chemical methods for oxidation also
exist, although they are not as prevalent in commercial production.
Some chemical oxidation methods suitable for polyol feedstocks
include oxidation with oxygen over metal catalysts (U.S. Pat. No.
2,472,168) and oxidation with chlorine or bromine with an aminoxyl
radical such as TEMPO (U.S. Pat. No. 6,498,269). Additional methods
employ nitric acid as the oxidizing agent in aqueous solution and
have been described (Kiely, U.S. Pat. No. 7,692,041). The skilled
artisan will appreciate that any of the methods described herein,
as well as any combination of the methods may be used to obtain the
hydroxycarboxylic acid.
[0027] The oxidation of a variety of feedstocks, including glucose
will generally produce a mixture of oxidation products that
includes gluconic acid, glucaric acid, tartaric acid, tartronic
acid, and glycolic acids, all of which are hydroxycarboxylic acids,
and within the scope of the current invention. It was surprisingly
found that the combination of the salts of the hydroxycarboxylic
acids discussed herein with a salt of boric acid provided corrosion
inhibition properties similar to the use of the combination of
hydroxycarboxylic acid salts alone. The use of hydroxycarboxylic
acids as a potential corrosion inhibitor has been previously
discussed (see U.S. Published Patent Application 2009/0250653);
however, combining the hydroxycarboxylic acid salts with an oxoacid
anion, such as borate has not previously been contemplated, due to
the fact that oxoacid anions, such as borate, are potentially
corrosive to metals, as evidenced by the corrosion tests performed
in Example 3 and 4. Specifically, the product mixture of multiple
(or a mixture of) hydroxycarboxylic acid salts with borate
performed comparable to pure glucarate with borate (see Example 1,
Table 1). Even more surprising was that the oxidation product with
borate performed comparable to the oxidation product without borate
or pure glucarate without borate. These findings were unexpected
since borate itself is more corrosive than water and since the
overall concentration of the hydroxycarboxylic acid salts is less
in the test solution when combined with borate than when tested
alone (in both cases the total concentration of the inhibitor in
the test solution was 0.09%).
[0028] The current invention also provides improved efficiencies
due to the fact that a portion of the glucaric acid salt may be
removed from the mixture of hydroxycarboxylic acid salts without
comprising the efficacy as a corrosion inhibitor. One of skill in
the art will appreciate that the ability to remove glucarate will
improve the cost-effectiveness of the product, and allow for
greater efficiencies in the manufacturing process.
[0029] The compositions of the current invention, including the
mixtures with multiple hydroxycarboxylic acid salts, were also
evaluated as a sequestering agent for calcium (see Example 9, Table
4). As seen with pure glucarate salts, the mixture alone proved to
be a poor sequestering agent. However, in conjunction with borate
salts, the sequestering ability significantly improved.
Accordingly, the compositions of the current invention provide both
corrosion inhibition, as well as metal sequestering properties.
[0030] The compounds and processes of the invention will be better
understood by reference to the following examples, which are
intended as an illustration of and not a limitation upon the scope
of the invention. Each example illustrates at least one method of
preparing various intermediate compounds and further illustrates
each intermediate utilized in the overall process. These are
certain preferred embodiments, which are not intended to limit the
present invention's scope. On the contrary, the present invention
covers all alternatives, modifications, and equivalents as can be
included within the scope of the claims and routine
experimentation.
Example I
Preparation of Corrosion Inhibitor Test Solutions
[0031] Corrosion tests were carried out using steel coupons
immersed in test solutions as described below. Test solutions were
prepared with deionized water. For inhibited test solutions, the
corrosion inhibitor was added to give a 0.09% concentration based
on dry weight. Solutions containing hydroxycarboxylic acid
salt/oxoacid anion salt corrosion inhibitors were prepared at
different weight ratios of the appropriate oxoacid anion salt to
hydroxycarboxylic acid salt.
Example 2
Corrosion Test Methods
[0032] Compounds and compound mixtures were evaluated as corrosion
inhibitors in aqueous solutions using a modified version of the
National Association of Corrosion Engineers (NACE) Standard
TM0169-95 laboratory immersion test. Distilled water was used to
prepare each solution and as a control standard. The effectiveness
of each corrosion inhibitor mixture was measured in both distilled
water and 3% sodium chloride (NaCl) solution. When corrosion
inhibition was measured in salt solution, a 3% solution of NaCl in
distilled water (300 g) was used as a salt reference. Each test
solution was prepared by dissolving the corrosion inhibitor (270
mg) in 300 mL of either distilled water or 3% NaCl solution to give
a 0.09% inhibitor solution. The pH of the inhibitor test solutions
was then made basic (pH 9-10) by the addition of 5% sodium
hydroxide.
[0033] Stamped and numbered steel TSI coupons which met the ASTM
F436 Type 1 requirement with a Rockwell hardness of C 38-45 were
used in the corrosion tests. Average coupon dimensions were 3.50 cm
outer diameter, 1.52 cm inner diameter, and 0.25 cm thickness with
a density of 7.85 g/cm', Prior to testing, the coupons were placed
in a sealed container on a rock tumbler with a non-abrasive
cleanser for 30 minutes to remove surface grease and impurities,
then wiped with acetone to remove any additional grease, rinsed
with deionized water, and acid etched with an 18.5% HC1 solution
for approximately 3 minutes. The coupons were rinsed with deionized
water, patted dry, placed in chloroform for 15 minutes, and then
allowed to air dry in a ventilated hood for 1 hour. Each coupon was
weighed to the nearest 0.1 mg at least two times to ensure a
consistent weight. Three cleaned and weighed coupons were attached
to a plastic bar suspended in a stoppered 500 mL Erlenmeyer flask
by a thin line through a hole in the stopper. A timed device raised
and lowered the test coupons so they were immersed in the test
solution for 10 minutes of each hour for a 72 hour period. Tests
were conducted at room temperature.
[0034] After the 72 hour test period, the coupons were removed from
solution, rinsed under tap water, and vigorously rubbed to remove
any surface corrosion material. The coupons were then placed in a
cleaning solution of concentrated hydrochloric acid containing 5%
stannous chloride and 2% antimony chloride. After 15 minutes, the
coupons were removed from the acid solution, rinsed vigorously
under tap water, and returned to the cleaning solution for an
additional 15 minutes. The coupons were again removed from the acid
solution, rinsed under tap water, rinsed under deionized water,
patted dry, and placed in a vessel containing chloroform for 10
minutes. The coupons were removed from the chloroform and allowed
to air dry under a ventilated hood for 1 hour before being weighed
to the nearest 0.1 mg. Each coupon was weighed twice, and the
weights were averaged. Corrosion rate in mils per year (MPY) was
calculated from the measured weight loss of each coupon using the
following equation:
M P Y = weight loss ( mg ) 534 area ( cm 2 ) time ( h ) metal
density ##EQU00001## metal density = 7.85 g / cm 3 ##EQU00001.2##
time = 72 hours ##EQU00001.3##
[0035] The MPY values of each of three coupons in the test solution
were averaged to determine the MPY value of the entire test
solution. The average corrosion rate for the control solution of
distilled H2O was also calculated and was subtracted from the MPY
value of each sample solution to give a corrected MPY value, which
is noted as MPY.sup.1.
Example 3
Corrosion Inhibition of Mixtures of Hydroxycarboxylic Acid Salts
and Oxoacid Anion Salts in Water
[0036] The effectiveness of mixtures of hydroxycarboxylic acid
salts and oxoacid anion salts were tested in distilled water, and
the results were compared to hydroxycarboxylic acid salts without
oxoacid anion salts (Table 1). Corrosion inhibitor test solutions
were prepared with boric acid and monopotassium D-glucarate (MKG),
and the pH of the test solutions were made basic with sodium
hydroxide. Sodium borate was prepared by neutralizing boric acid
with sodium hydroxide to pH 9. In all cases, the total
concentration of corrosion inhibitor in the test solution was
0.09%.
TABLE-US-00001 TABLE 1 Corrosion Rates (MPY) and Corrected
Corrosion Rates (MPY.sup.1) of Corrosion Inhibitors in Distilled
Water Corrosion Inhibitor MPY MPY.sup.1 None (H.sub.20 control)
1.97 0.000 100% Sodium borate 2.97 1.00 100% Monopotassium
D-glucarate 0.98 -0.99 (MKG) 80% MKG/20% boric acid 1.01 -.096 50%
MKG/50% boric acid 2.22 0.25
Sodium borate is not an effective corrosion inhibitor and has a
higher MPY corrosion rate than distilled water, thus giving a
corrected MPY.sup.1 rate greater than zero. Neutralized MKG is an
effective corrosion inhibitor with an MPY.sup.1 value less than
zero. The surprising result was that combinations of glucarate and
borate also serve as effective corrosion inhibitors giving negative
MPY.sup.1 values despite the fact that the amount of glucarate in
the mixture is less than 100% and that borate is more corrosive
than water. In the case of neutralized 80% MKG and 20% boric acid,
the corrosion inhibition effectiveness is comparable to neutralized
MKG alone.
Example 4
Corrosion Inhibition of Mixtures of Hydroxycarboxylic Acid Salts
and Oxoacid Anion Salts in 3% Sodium Chloride
[0037] The effectiveness of mixtures of hydroxycarboxylic acid
salts and oxoacid anion salts were tested in 3% sodium chloride,
and the results were compared to hydroxycarboxylic acid salts
without oxoacid anion salts (Table 2). Corrosion inhibitor test
solutions were prepared with borax (sodium borate), sodium
molybdate, sodium aluminate, or mixtures thereof as the oxoacid
anion salt component and with monopotassium D-glucarate (MKG), zinc
glucarate, sodium gluconate, xylaric acid, or galactaric acid as
the hydroxycarboxylic acid salt component. In each case, the pH of
the test solutions were made basic with sodium hydroxide, and the
total concentration of corrosion inhibitor in the test solution was
0.09%.
TABLE-US-00002 TABLE 2 Corrosion Rates (MPY) and Corrected
Corrosion Rates (MPY.sup.1) of Corrosion Inhibitors in 3% Sodium
Chloride Solution Corrosion Inhibitor MPY MPY.sup.1 H.sub.20
(control) 3.28 0.000 NaCl (control) 58.04 54.76 100% Sodium borate
61.54 58.26 100% Monopotassium D-glucarate 24.87 21.59 (MKG) 80%
MKG/20% sodium borate 28.99 25.71 80% Zinc glucarate/20% borate
14.67 11.39 80% MKG/20% sodium molybdate 24.96 21.68 50% MKG/50%
sodium molybdate 30.75 27.47 64% MKG/16% sodium molybdate/ 25.00
21.72 20% sodium borate 100% Sodium aluminate 30.56 27.28 67%
MKG/33% sodium aluminate 29.29 26.01 100% Sodium gluconate 29.56
26.28 80% Sodium gluconate/20% sodium 31.82 28.54 borate 100%
Xylaric acid 32.33 29.05 80% Xylaric acid/20% sodium borate 34.06
30.78 100% Galactaric acid 25.92 22.64 80% Galactaric acid/20%
sodium borate 28.27 24.99
[0038] As seen in Table 2, sodium borate is not an effective
corrosion inhibitor in sodium chloride and is actually more
corrosive than 3% sodium chloride alone. The mixtures of sodium
borate and various hydroxycarboxylic acid salts all show slightly
higher but comparable corrosion rates as compared to the
hydroxycarboxylic acid salts alone. Again, the surprising result
was that the mixtures of hydroxycarboxylic acid salts and borate
also serve as effective corrosion inhibitors despite the fact that
the mixture contains less hydroxycarboxylic acid salt and that
borate is a corrosive agent. The mixtures of hydroxycarboxylic acid
salts and borate have the added benefit of providing much higher
calcium sequestering properties compared to the hydroxycarboxylic
acid salts alone (Table 4). The results of Table 2 also illustrate
the use of zinc glucarate in combination with sodium borate as a
corrosion inhibitor. Zinc salts are known corrosion inhibitors;
however, the use of zinc glucarate is limited due to its low water
solubility. The addition of borate increases the water solubility
of zinc glucarate and therefore improves the corrosion inhibiting
properties of the mixture.
[0039] Sodium aluminate alone is a corrosion inhibitor and mixtures
with glucarate also show corrosion inhibiting properties. The
mixtures, however, have the added advantage of high performance as
calcium sequestering agents compared to either glucarate or
aluminate alone (Table 4).
Example 5
Preparation of Glucarate Mixture 1
[0040] Glucarate mixture 1 was prepared by the nitric acid
oxidation of glucose as described in U.S. Pat. No. 7,692,041. After
removal of nitric acid from the oxidation mixture, the organic acid
products were neutralized with sodium hydroxide to give glucarate
mixture 1. The amounts of the sodium salts of glucaric acid,
gluconic acid, and tartaric acid in glucarate mixture 1 are given
in Table 3.
Example 6
Preparation of Glucarate Mixture 2
[0041] Dextrose was oxidized and nitric acid was separated as
described in U.S. Pat. No. 7,692,041. The resulting oxidation
product mixture was neutralized to a pH of 3.5 with aqueous
potassium hydroxide which produced a precipitate. The solid
precipitate was isolated by filtration, and the filtrate was
neutralized with aqueous sodium hydroxide to a pH of 9 to give
Glucarate mixture 2. The amounts of the sodium salts of glucaric
acid, gluconic acid, and tartaric acid in glucarate mixture 2 are
given in Table 3.
Example 7
Preparation of Glucarate Mixture 3
[0042] Sodium gluconate (0.27 g) was added to glucarate mixture 2
(10.1 g, 20% w/w) to give glucarate mixture 3. The amounts of the
sodium salts of glucaric acid, gluconic acid, and tartaric acid in
glucarate mixture 3 are given in Table 3.
Example 8
Corrosion Inhibition of Mixtures of Multiple Hydroxycarboxylic Acid
Salts and an Oxoacid Anion Salt
[0043] The effectiveness of mixtures of multiple hydroxycarboxylic
acid salts and oxoacid anion salts were tested in distilled water
and in 3% sodium chloride and the results were compared to mixtures
of multiple hydroxycarboxylic acid salts without an oxoacid anion
salt (Table 3). Corrosion inhibitor test solutions were prepared
with either borax (sodium borate) or sodium aluminate, as the
oxoacid anion salt component and with glucarate mixtures 1-4 (see
Example 5-7) as the hydroxycarboxylic acid salt component. In each
case, the test solution was made basic with sodium hydroxide, and
the total concentration of corrosion inhibitor in the test solution
was 0.09%.
TABLE-US-00003 TABLE 3 Corrosion Inhibition of Mixtures of Multiple
Hydroxycarboxylic Acid Salts and Borate % % % % Glucarate Gluconate
Tartrate Oxoacid Sample Salt Salt Salt Anion Salt MPY H.sub.20 0 0
0 0 3.28 Glucarate 60 25 5 0 1.13 .sup.a Mixture 1 Glucarate 48 20
4 20 0.45 .sup.a Mixture 1/ sodium borate Glucarate 42 18 3.5 30
0.67 .sup.a Mixture 1/ sodium borate Glucarate 60 25 5 0 24.10
.sup.b Mixture 1 Glucarate 48 20 4 20 29.31 .sup.b Mixture 1/
sodium borate Glucarate 42 18 3.5 30 31.32 .sup.b Mixture 1/ sodium
aluminate Glucarate 50 30 6 0 27.06 .sup.b Mixture 2 Glucarate 40
24 5 20 32.50 .sup.b Mixture 2/ sodium borate Glucarate 20 62 2 10
30.53 .sup.b Mixture 3/ sodium borate 3% NaCl 0 0 0 0 58.04 .sup.a
Corrosion rate measured in distilled water. .sup.b Corrosion rate
measured in 3% sodium chloride solution.
[0044] The results in Table 5 demonstrate the efficacy of mixtures
of hydroxycarboxylic acid salts including glucarate, gluconate, and
tartrate as corrosion inhibitors. These results also demonstrate
the synergistic relationship between glucarate, gluconate, and
tartrate with borate in solution. In general, mixtures with higher
levels of glucarate perform better than those with less glucarate;
however, glucarate mixture 1 showed improved corrosion inhibition
in sodium chloride solution compared to the solution of pure
glucarate (Table 2). Further, the corrosion results for all
solutions were similar to those obtained by the pure glucarate
solution, suggesting that the replacement of some of the glucarate
with other hydroxycarboxylates such as gluconate and tartrate
provides a useful alternative to corrosion inhibiting solutions
containing pure glucarate. Even the solutions incorporating borate
showed similar efficacy for corrosion inhibition, which was
surprising given the fact that borate is known to be corrosive and
that the level of glucarate was reduced in these mixtures.
Example 9
Calcium Sequestration Capacity
[0045] The calcium chelating ability of various compounds and
mixtures was determined by an established procedure (Wilham, 1971).
Briefly, the sequestering agent (1.0 g dry weight) was dissolved in
deionized water and diluted to 50 mL. The pH of the solution was
adjusted to 10 with 45% aqueous sodium hydroxide, followed by the
addition of 2% aqueous sodium oxalate (2 mL). The test solution was
titrated to slight turbidity with 1% aqueous calcium acetate. Each
mL of 1% calcium acetate is equivalent to 6.32 mg of CaCO.sub.3.
Results from the sequestration tests are given in Table 4. It is
evident from the results in Table 4 that hydroxycarboxylic acid
salts alone are poor sequestering agents for calcium given the low
values for mg CaCO.sub.3 per g of sequestering agent; however
through the addition of suitable oxoacid anion salts such as sodium
borate, the sequestering capacity is greatly improved.
TABLE-US-00004 TABLE 4 Calcium Sequestration of Various Compounds
and Compound Mixtures at pH 10 and 25.degree. C. mg CaCO.sub.3/
Sequestering Agent g of compound 100% Sodium potassium D-glucarate
(SPG) 25.6 100% Glucarate mixture 1 24.6 100% Glucarate mixture 2
38.9 100% Sodium borate 12.3 90% SPG/10% sodium borate 158 80%
SPG/20% sodium borate 219 60% SPG/40% sodium borate 190 20% SPG/80%
sodium borate 64.5 80% SPG/20% sodium aluminate 303 .sup.a 70%
SPG/30% sodium aluminate 315 .sup.a 90% Glucarate mixture 1/10%
sodium borate 114 85% Glucarate mixture 1/15% sodium borate 145 80%
Glucarate mixture 1/20% sodium borate 150 75% Glucarate mixture
1/25% sodium borate 138 70% Glucarate mixture 1/30% sodium borate
139 60% Glucarate mixture 1/40% sodium borate 129 20% Glucarate
mixture 1/80% sodium borate 63.2 70% Glucarate mixture 1/30% sodium
aluminate 235 .sup.a 80% Glucarate mixture 2/20% sodium borate 140
60% Glucarate mixture 2/40% sodium borate 121 20% Glucarate mixture
2/80% sodium borate 62.4 .sup.a Calcium sequestration measured at
pH 11
* * * * *